Why can’t you pick mushrooms, berries along the road?

Every summer people pick mushrooms and berries in the forest. Most of them go far into the forest, the farther from the road the crops are harvested, the less likely they are to get poisoned. Mushrooms and berries are able to absorb and accumulate exhaust gases, heavy metal salts. In places where cars pass or railway tracks pass, there are especially many of them, soil and air are polluted. All this is dangerous for humans. If you eat such a mushroom or berry, you can get poisoned or get sick with serious diseases.